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Stress Physiology of Grey-Faced Petrels: interannual measures of feather corticosterone as a conservation tool

*Míra Fessardi1, Brendon J. Dunphy1; Todd Landers2, Kristal Cain1

1School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.;;

2Auckland Council, Auckland.

*Master’s student

Seabirds are the most threatened group of birds globally, and of critical ecological importance to ocean ecosystems. Breeding seabirds are touted as a potential low-cost bioassay of ocean health as reductions in ocean productivity influence foraging opportunities and increase bird stress. Accordingly, stress hormones (i.e., corticosterone/CORT) often show a strong link to food supply, suggesting they are useful tool for linking climate change, foraging conditions and seabird demographics. Because higher CORT levels in chicks experiencing stress are deposited in developing feathers, measures of feather CORT may provide useful estimates of the consequences of environmental stressors. This study investigated whether variation in Grey-faced petrel (Pterodroma gouldi) feather CORT can be used as a proxy of ocean conditions and as a monitoring tool for population breeding success. Reproductive success and feather CORT levels were obtained from chicks at Ihumoana Island over four years (2017, 2019-2021). These were matched to relevant remote sensing data to investigate whether feather CORT reflects changes in ocean conditions, and to measurements of feather quality and breeding success ((sea surface temperature and primary productivity) i.e., chick’s body condition, fledging success for laid eggs). We found that chick stress levels fluctuated among seasons, but variation was not closely tied to ocean conditions. Productivity and fCORT were also not tightly coupled, however, increased fCORT and lower feather quality (brightness) predicted reduced breeding success. Taken together these measures offer a promising tool for seabird conservation.